PROJECT SUMMARY In the past two decades, the rate of opioid use disorder (OUD) among pregnant women has more than quadrupled, constituting a U.S. public health crisis. For affected women and their children, OUD presents a unique set of healthcare challenges across a continuum of care, with most research on this population focused on pregnancy and the birth hospitalization. However, within a primary care setting, there remains a lack of rigorous research on how best to support mothers with OUD and their children given the complexity of their medical and psychosocial care needs. The current paradigm of well child care (WCC) comprised of 15-minute pediatric visits provides limited opportunity for building maternal trust, addressing information needs, and engaging mothers as key participants in their child?s health. The objective of this project is to develop and evaluate a comprehensive group model of WCC for mothers with OUD and their children that is clinically tailored for opioid-exposed infants, is trauma informed, and is embedded within a maternal OUD treatment program. As a novel alternative to routine care, group well child visits consist of a 2-hour facilitated session with several mothers and their infants grouped together, resulting in increased time with the pediatrician, peer-to-peer learning, and enhanced focus on behavior change and self-care. All study procedures will occur at the Maternal Addiction Treatment Education & Research (MATER) program at Thomas Jefferson University, which provides comprehensive medical and behavioral health programming for pregnant and parenting women with OUD. In Aim 1, we will develop and standardize a modular, manualized group-based well child care curriculum for this population, using an iterative, qualitative process of feedback from patients and providers. In Aim 2, we will demonstrate the feasibility and acceptability of implementing group WCC within a maternal OUD treatment program. One hundred and eight mother-infant dyads will be randomized to either group well child care or traditional well child care, and studied over the first 18 months of life. Qualitative and quantitative data from patients and treatment center staff will be collected. Finally in Aim 3, we will evaluate the efficacy of group WCC to improve WCC utilization and experience and parenting knowledge and quality compared with traditional WCC. This project responds to AHRQ's special emphasis notice of interest for health services research on the opioids crisis (NOT-HS-18-015) by addressing the experience and outcomes of women and children, AHRQ priority populations. This project also responds to AHRQ?s interest in primary care innovations to address social determinants of health (NOT-HS-19-011). Given the volume of children affected by maternal OUD who incur higher risks of maladaptive parenting, intergenerational effects of trauma, and adverse health outcomes, we anticipate this research will be of significant impact.